The term "screeding" includes spreading, distributing, smoothing and leveling uncured concrete that has been placed or poured, but can also apply to other loose, spreadable materials such as sand and gravel. The present development relates to a vehicle which is positioned adjacent the uncured concrete, or driven through the uncured concrete, while screeding the material adjacent the vehicle without using prepositioned guides or rails.
A number of methods and techniques for spreading and leveling concrete have been developed and are part of the prior art. The simplest of these involves the passing of the edge of a two-by-four plank across the top of the poured concrete, but there are also more sophisticated power screeds. In the construction of bridges or highways, and also for large concrete floor areas like those in warehouses, large rail or guide supported screeds are typically used. These screeds employ long trusses or beams which span the width of the concrete area to be formed, and ride on heavy guides or rails adjacent opposite sides of the concrete area.
Certain prior art developments are worth noting, and the following is a list of related prior art patents.
U.S. Pat. No. 4,655,633, issued Apr. 7, 1987 to Somero et al.
Canadian patent 1,203,707, issued Apr. 29, 1986 to Allen.
Canadian patent 1,016,380, issued Aug. 30, 1977 to Fisher et al.
Canadian patent 931,001, issued Jul. 31, 1973 to McGregor.
Canadian patent 1,088,362, issued Oct. 28, 1980 to Rowe.
Canadian patent 1,174,071, issued Sep. 11, 1984 to Miller.
All of the prior developments suffer from various disadvantages and shortcomings, and it is a general object of the present invention to provide an improved, mobile, self-propelled screeding apparatus capable of reliably carrying out all of the tasks of a typical screeder, while providing increased manoeuverability and control.
In particular, this invention aims to provide an improvement over what is taught in U.S. Pat. No. 4,655,633, mentioned above. This prior patent suffers from a number of disadvantages, which it is the aim of this invention to overcome. Firstly, the prior patent (hereinafter referred to as Somero et al) provides a boom in the form of a truss, mounted in rail fashion to slide as a unit with respect to the main frame. The sliding movement is carried out by a chain drive, thus introducing a mechanical device (the chain) which is particularly subject to breaking down. Further, Somero et al drives all of his wheels from a single hydraulic motor, which means that if that motor breaks down, then the entire drive mechanism is disabled.
Another problem is that Somero et al drive the auger by a chain which connects it to a distant drive source. Again, the chain is a weak mechanical device, subject to break-downs.
Finally, Somero et al introduce an unnecessary complication by requiring the screed assembly to move along the boom, with the boom stationary and fixed in place with respect to the main frame. This requires a carriage for the screed assembly, so that it can move along the boom, thus constituting a complex mechanism that could easily break down.
By contrast, in a preferred embodiment, the present invention provides a telescoping boom which is driven by hydraulic cylinders, thus providing an extremely simplified method of moving the screed assembly toward and away from the main frame. Further, this invention provides separate hydraulic motors for each of the wheels, so that if one or more should break down, the others can still be used.
Further, in a preferred embodiment, the present invention provides an auger driven by a hydraulic motor located directly adjacent the auger. This simplifies the mechanical construction, and reduces the risk of break-down.
Finally, in a preferred embodiment, the screed assembly in the present invention does not move along the boom, but rather is fixed with respect to a sliding member that is part of the telescoping assembly. This simplifies the apparatus.
More particularly, this invention provides a self-propelled screeding apparatus for placed and/or poured, uncured concrete or the like previously placed on the ground or another support surface, the apparatus comprising:
a frame,
propulsion means on said frame for moving said frame over the ground or support surface;
a platform mounted above said frame for rotation with respect thereto,
longitudinal sleeve means incorporated into said platform,
a boom, the boom being a telescoping boom that includes at least one longitudinally slidable means mounted for sliding movement within said longitudinal sleeve means, and hydraulic cylinder means for causing the longitudinally slidable means to move longitudinally with respect to the longitudinal sleeve means;
screed means for spreading and/or smoothing the loose or plastic material; and
screed mounting means for mounting said screed means on said boom.